• 한국전산유체공학회지
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• 제11권3호
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• pp.28-36
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• 2006

NSBT(No Slip Boundary Treatment) is a newly developed scheme for the treatment of a no slip condition on the solid wall of obstacle in a flow field. In our research, NSBT was used to perform LBM simulation of a flow over a circular cylinder to determine the flow feature and aerodynamics characteristic of the cylinder. To ascertain the applicability of NSBT on the complex shape of the obstacle, it was first simulated for the case of the flow over a circular and square cylinder in a channel and the results were compared against the solution of Navier-Stokes equation. The simulations were performed in a moderate range of Reynolds number at each cylinder position to identify the flow feature and aerodynamic characteristics of circular cylinder in a channel. The drag coefficients of the cylinder were calculated from the simulation results. We have numerically confirmed that the critical reynolds number for vortex shedding is in the range of 200$\sim$250. For the gap parameter $\gamma$ = 2 cases at Re > 240, the vortex shedding were symmetric and it resembled the Karmann vortex. As the cylinder approached to one wall, the vorticity significantly reduced in length while the vorticity on the other side elongated and the vorticity combined with the wall boundary-layer vorticity. The resultant $C_d$ by LBM concurred with the results of DNS simulation performed by previous researchers.

• 한국안전학회지
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• 제33권5호
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• pp.134-140
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• 2018

Scour in the downstream of hydraulic structures such as apron induces to collapse due to abruptly increasing rainfall and discharge in streams and reaches. This is because the forcible jet from overflowing is not sufficiently dissipated by existing energy dissipators, and it continues to sweep the bed materials during flood events. In this study, a second stilling basin was proposed as a countermeasure and the energy dissipation efficiency of this structure was analyzed using 3D-dimensional numerical analysis. First, results from previous research and hydraulic tests were used to verify the accuracy of the numerical model. It showed that the second stilling basin played a definite role in reducing the bottom velocity, comparing with diminishing the energy dissipation when numerical tests were conducted under scaled field conditions in Korea. This means that the second stilling basin can be a countermeasure against scour in downstream. If more efficiency analysis of the second stilling basin would be performed in terms of energy dissipator for various types of hydraulic jump, it would be an alternative solution to scouring issues.

• 마이크로전자및패키징학회지
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• 제8권2호
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• pp.43-48
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• 2001

Economical consumption of energy, longer life of lamps, higher lighting comfort and new aesthetic of illumination is subject of numerous research and development works. The halogen lamps are an example of positive solution some of above mentioned problems. The electronic transformers are more frequent used for their supply. In comparison with conventional transformers they have less weight, less volume and 60% less power losses. Their advantages are particular visible, when the hybrid technique is applied. The paper presents the results of engineering research and development works carried out in Private Institute of Electronic Engineering, in R. & D. Center for Hybrid Microelectronics and Resistors and in Technical School of Communications in Krakow, in the field of the design and exploitation tests of hybrid converters 220V AC /12V DC (electronic transformers) and electronic ballasts destined for the supply of halogen lamps 20W to 150W and fluorescent lamps respectively. To perform the converters, thick film technology and surface mount technology were used. For the protection of converter electronic circuit the thick film temperature sensor and transistors were applied. Moreover the paper presents the base application circuits of elaborated converters, their technical parameters and exploitation results. The development perspectives of such domain of hybrid circuits are also discussed.

• 통상정보연구
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• 제7권3호
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• pp.3-25
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• 2005

It is high time to prepare the online publication system of academic research paper. Online publications like digital research paper, e-Book, etc. are increased day by day as the information technology(IT) is developing continually. But, the legal aspect of publication system of academic research paper in Korea is not prepared yet. The purposes of this study are to examine the problems on the publication system of academic research paper in the context of digital goods and to frame a policy of legal proceedings in relation to the social science. The methodology used in this paper is theoretical analysis which is examining the case of academic research system and scientific journal in Korea. As a result of this study, following measures are suggested: (1) Legal provisions on the online publication system, that is, "Research Promotion Law of Korea" controlled by KRF(Korea Research Foundation) and MOE(Ministry of Education) should be revised. (2) Solution like software program and DB system proceeding the data on academic research paper should be prepared newly. (3) From the viewpoint of digital goods, both protecting the intellectual property right and settling the reliance upon online publication system should also be considered simultaneously.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1801-1809
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• 2000

A study on the topology optimization of Hard-Disk-Driver(HDD) actuator arm in free vibration is presented. The purpose of this research is to increasse the natural frequency of the first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of high speed actuator am. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, the smoothly-varying density field is obtained without checker-board patterns incurred. As a result of the study an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode or the suggested design is subsequently increased over the existing one.

• 한국건축시공학회지
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• 제20권6호
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• pp.577-584
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• 2020

Construction automation and robotics have been widely adopted in the construction industry as a promising solution to such issues like a shortage of skilled labor and the difficulties workers face in harsh working environments. The analysis of the knowledge structure and its evolution from the existing articles helps identify essential knowledge elements and possible future research directions. This study attempts to (1) construct keyword networks from the papers published in the International Symposium on Automation and Robotics in Construction (ISARC), (2) investigate how keywords and keyword communities are associated with each other, and (3) examine the changes in the crucial keywords over time. Through cluster analysis, 79 keywords were categorized into four groups (BIM, Building construction, Sensing, and GPS as representative keywords) with similar structural positions. Research trends show that research themes related to Infrastructure, Construction equipment, and 3D have consistently received a large amount of attention, regardless of geographical region. Research on as-built status model utilization through BIM and Laser scanning and improving Energy performance is taking place more frequently. In contrast, research studies related to problem-solving based on Neural networks are not as common as previously. This study provides useful insights into the construction automation field, at both the macro and micro levels.

• 한국작물학회지
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• 제21권1호
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• pp.97-124
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• 1976

우리나라 감자 춘하작물재배의 주장려품종이고 휴면기간이 긴 남작(Irish Cobbler)을 추작할때 효과적인 최아처리법을 구명하기 위하여, 대관령산종서를 고려대학교 농과대학 실험농장에시 춘작 증식하여 추작용종서로 사용하고, 1974 및 '75의 양년도에 걸쳐서 농대구내수음하 설치한 최아상(그림 1)에서 구당 60편의 3반복 난괴법으론 최아시험을 실시하고, 실험농장 포장에서 구당 1.8$m^2$(15주)의 3반복 난괴법으로 포장재배시험을 실시한 성적을 요약하면 다음과 같으며, 시험기간(1975년)중의 기상개요는 그림 2와 같았다. 1. 최아처리법과 발아(부표 1~7, 그림 3~5) (a) GA(Gibberellin)처리는 발아가 빨라서 7~8일 에 발아하여 최아소요일수가 약 10일이며, 발아가 균일하고, 부패가 적어 건전발아개체비율도 높으나, 편당발아본수가 3~4본으르 많고, 싹이 세장하며 발근이 없었다. (b) Ethrel처리는 발아가 훨씬 GA보다 늦어서 대체로 최아소요일수가 20~25일이며, 발아의 균일성과 부패및 건전발아개체비율에서 GA보다 고간 못하나, 편당발아본수가 1~2본으로 적고 싹이 단태건실하며 발근이 극히 양호하였다. (c) GA와 Ethrel의 혼합처리는 GA처리보다 1~2일 발아가 늦으나 싹은 비교적 건실하며, 그밖의 발아상은 GA처리와 거의 같았다. (d) Ethylene Chlorohydrin처리는 Ethrel처리와 거의 같은 발아상을 보이나 발아에 23~26일이 소요되고, 최아중의 부패도 많았다. (e) 6-Benzyladenine처리는 Ethrel처리처럼 싹이 단태건실하고 편당발아본수도 1~2본으로 적으며, 발근도 보이나 발아에 22~28일이 소요되고. 발아가 균일하지 못하며, 절단하여 처리할 경우에는 부패가 심해질 우려가 컸다. (f) 약제별 최적처리법은 다음과 같이 보였다. GA처리 : 절단서면 1~2ppm, 전형서면 2~5ppm에 60분처리. Ethrel처리 : 절단서면 500ppm, 전형서면 1000~2000ppm에 60분처리. GA와 Ethrel의 혼합처리 : 절단서면 GA 1~2ppm＋Ethrel 250~500ppm, 전형서면 GA 5ppm＋Ethrel 250~500ppm, 60분처리. 2. 처리법과 부패 (a) 18~24시간의 GA처리는 거의 완전한 부패를 초래하였다(표 2) (b) Ethylene Chlorohydrin처리는 심한 부패를 유발하고(표 2), 6-Benzyladenine처리도 많은 부패를 유발하는(부표 7) 경향이 보였다. (c) 처리중에 교반하여 표피가 갈리게 한것은 전량 부패하였다(부표 1) (d) 종서에 칼로 3-4곳에 자상을 내서 GA처리를 한 것은 발아조장의 효과가 없고, 부패를 조장하는 경향이 보였다(부표 1) 3. 상토와 발아(부표 1) (a) 최아상의 상토로써 부식질세토를 사용하였을 경우에는 사상의 경우보다 부패가 없고 발아도 양호 하였다. (b) 사상의 경우에는 세사보다 조사가 양호하였다. 4. 처리시기와 발아 (a) 7월 15일처리에 비하여 8월 24일처리의 경우에 Ethrel의 전형서처리에서는 발아가 4일 빨랐으나, Ethrel 절단서처리 및 GA처리에서는 발아가 거의 빨라지지 않았다(그림 9) (b) 처리시기가 늦어져서 휴면이 경과될수록 발아와 발근이 조장되는 경향이 보였다(부표 8) (c) 최아기간이 매우 고온건조하였던 경우(8월 14일처리)에는 심한 부패를 보였다(그림 10) 5. 처리법 및 정식기와 수량 (a) 정식기를 같게 할 경우의 수량은 Ethrel>GAㆍEthrel 혼합>GA 처리의 순위로서 정식당시의 싹의 건실도 및 발근상태와 깊은 관련이 있어보였다. Ethylene Chlorohydrin처리는 포장결주가 많아서 수량이 적었다(그림 11) (b) 처리기를 같게 하여 정식기가 GA보다 Ethrel 처리가 15일 늦어 질 경우에는 Ethrel이 GA처리보다 감수경향을 보였다(부표 10) (c) 어느 처리에서나 정식기가 빠를수록 증수되는 경향이 보였다(부표 10) (d) GA처리 조식의 경우에는 고간 도장하는 경향이 보였으나, 기타처리 및 GA처리라도 만식의 경우에는 도장이 보이지 않았다(그림 12)

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1433-1438
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• 2006

An AsFlFFF channel was designed and built, and then tested for analysis of pullulans and proteins. Pullulans and proteins having various nominal molecular weights were injected at various conditions of the cross-flow rate ($F_c$) and the channel-out flow rate ($F_{out}$). The retention (measured by the retention ratio R) and the zone broadening (measured by the plate height H) were measured, and then compared with theory. When the incoming flow rate, $f_{in}$ (and thus $F_{out}$) was varied with $F_c$ fixed at 2.5 mL/min, the plate height measured for the pullulan with nominal molecular weight (M) of about 100,000 showed the trend expected by the longitudinal diffusion theory (H decreases with increasing flow rate). In contrast, when $F_{out}$ was varied with the flow rate ratio, $F_c/F_{out}$, fixed constant at 5, the plate height measured for the same sample showed the trend expected from the non-equilibrium theory (H increases with increasing flow rate). Calibration plots (log D vs. log M) obtained with pullulans and proteins were not coincide, probably due to the difference in molecular conformation, suggesting the analysis of pullulans and proteins using AsFlFFF requires independent calibration. It was found that the linearity of the protein-calibration plot was improved by using a buffer solution as the carrier.

• 대한핵의학회지
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• 제38권4호
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• pp.318-324
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• 2004

목적: Philips GEMINI PET/CT 스캐너는 GSO 섬광결정을 사용해 제작된 전신용 PET/CT 스캐너이다. 이 연구에서는 NEMA에서 새롭게 제안한 NEMA NU2-2001에 따라 GEMINI PET/CT 스캐너의 공간분해능, 민감도, 산란분획, NECR 등을 평가하고 그 결과를 BGO, LSO등의 섬광결정의 특성과 비교하였다. 대상 및 방법: GEMINI는 Philips ALLEGRO PET과 MX8000 D multi-slice CT 스캐너를 결합한 PET/CT 스캐너로서 검출기는 GSO 섬광결정 ($4{\times}6{\times}20mm^3$)을 사용하였고 축방향 시야는 18 cm이다. 공간분해능. 민감도, 산란분획, NECR 등을 평가하기 위하여 PET 데이터를 획득하였다(동시계수창: 8 ns, 에너지창: $409{\sim}664$ keV). 공간분해능 측정을 위하여 축횡단면의 중심에서 1 cm, 10 cm 떨어진 지점의 각 3지점((a) x=0, y=1, (b)x=10, y=0, (c)x=0, y=10)에서 영상을 획득한 다음 여과후역투사방법(램프필터 사용)과 3D RAMLA를 이용하여 영상재구성을 하고 FWHM을 구하였다. 민감도 측정을 위하여 선선원(F-18)을 축횡단면의 중심과 중심에서 10 cm 벗어난 지점에서 5개의 알루미늄관을 차례로 씌워 매질감쇠에 따라 달라지는 참계수를 구하고 이 값을 회귀분석하여 감쇠매질이 없는 이상적인 상황에서의 민감도를 측정하였다(랜덤계수가 참계수의 1%이내). 산란분획과 NECR을 측정하기 위하여 F-18 선선원(1110 MBq)을 산란팬텀에 주입하여 7반감기동안 계수를 획득하였다. SSRB을 사용하여 3D 데이터를 재구성한 다음 랜덤계수율이 참계수율이 1% 미만인 영역에서 산란분획을 구하고 각 횡단면의 값을 평균하여 전체 산란분획을 얻었다. 이 값을 기초로 각 프레임, 각 횡단면에 대한 랜덤계수율, 산란계수율, NECR을 구하였다. 결과: 스캐너의 중심에서 1 cm 벗어난 지점에서 횡축방향, 축방향 공간분해능은 (1) 5.3, 6.5 mm (FBP), (2) 5.1, 5.9 mm (3D RAMLA)이었다. 횡단면의 중심에서 10 cm 벗어난 지점에서 횡축반경방향, 횡축접선방향, 축방향 공간분해능은 (1) 5.7, 5.7, 7.0 mm (FBP), (2) 5.4, 5.4, 6.4 mm (3D RAMLA)이었다. 감쇠매질이 없는 이상적인 상황에서의 민감도는 횡단면의 중심에서 3,620 counts/sec/MBq, 횡단면의 중심에서 10 cm 벗어난 지점에서 4,324 counts/sec/MBq이었다. 산란분획은 40.6%, 최대 참계수율과 최대 NECR은 각각 88.9 kcps @ 12.9 kBq/mL, 34.3 kcps @ 8.84 kBq/mL이었다. 결론: 이 실험에서 NEMA NU2-2001을 이용해 GSO 섬광결정을 사용해 제작된 PET/CT에 대한 성능 평가를 실시하였다. 이는 BGO, LSO 섬광결정을 사용해 제작된 PET 스캐너의 특성과 비교할 수 있는 자료를 제공하며 PET 영상 획득 시 객관적 평가와 분석에 유용하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.271-271
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• 2006

The structural, dielectric and piezoelectric properties of $[Bi_{1-x}(Na_{0.7-x}K_{0.2}Li_{0.1})]_{0.5}BaxTiO_3$ (BNKLBxT) ceramics were studied for the compositional range, x = 0-0.08. The samples were prepared by conventional sintering technique. The result of X-ray diffraction (XRD) suggest that $Ba^{2+}$ diffuse into the $[Bi(Na_{0.7}K_{0.2}Li_{0.1})]_{0.5}TiO_3$ (BNKLT) lattices to form a solid solution with a single phase perovskite structure. The ceramic show excellent piezoelectric and ferroelectric properties, and optimum properties measured are as follows: piezoelectric constant $d_{33}=230pC/N$, planar electromechanical coupling factor $k_p\;=\;40.3%$, remanent polarization $P_r\;=\;30\;{\mu}C/cm^2$, and coercive field $E_c\; =\;2.5\;kV/mm$, respectively.